All Aquarium Calculators
Free tools that do the maths for your tank — volume, medication dosing, bioload stress, substrate, stocking density, Walstad soil, nano planning, and bowl setup. No signup, no paywall, runs entirely in your browser.
Tank Size Calculator
Calculate your tank's exact water volume in gallons and litres. Supports rectangular, bowfront, and hexagonal shapes.
Most popularMedication Dosing Calculator
Convert tank volume, target ppm, and chemical concentration into an exact mL or teaspoon dose. Works for Prime, PraziPro, ParaGuard, Excel, and pure powders.
NewBioload Stress Calculator
Enter your current + proposed fish to get a 0–100 Bioload Stress Score and a specific filtration turnover recommendation. Smarter than inch-per-gallon.
NewSubstrate & Gravel Calculator
Get exact pounds or kilograms of gravel, sand, aquasoil, or soil for any tank footprint and depth. Includes substrate-specific density factors.
NewFish Stocking Calculator
How many fish can your tank safely hold? Uses bioload, surface area, and filtration — not the outdated inch-per-gallon rule.
EssentialNano Stocking Wizard
Get a curated stocking plan for tanks under 60 litres. Picks compatible species based on your tank size and experience level.
For small tanksWalstad Soil Calculator
Calculate exactly how much soil and cap material you need for a Walstad-method planted tank. No guessing, no waste.
Planted tanksWalstad Bowl Planner
Plan a self-sustaining Walstad bowl — soil, plants, stocking, and maintenance schedule tailored to your bowl size.
Low-techBristlenose Genetics Calculator
Predict offspring colours and fin types from bristlenose pleco breeding pairs. Covers albino, longfin, and super-red genetics.
For breedersNano Cichlid Stocking Calculator
Check bioload and compatibility for dwarf cichlids — Apistogramma, rams, shell dwellers, and kribensis in 20–40 gallon tanks.
For cichlid keepersWhich calculator do I need?
Just starting out? Run the Tank Size Calculator first to find your real water volume, then the Bioload Calculator to plan your fish list with a stress score and filtration recommendation.
Setting up a new tank? Use the Substrate Calculator to buy the right amount of gravel, sand, or aquasoil, then the Walstad Soil Calculator if you're going dirted.
Treating sick fish? The Medication Dosing Calculator converts ppm targets and chemical concentrations into exact mL or teaspoon doses — no more capful guessing.
Small tank (under 60 L)? The Nano Stocking Wizard gives you ready-made stocking plans tuned for nano tanks.